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iDirect: Tech Brief - QoS and DVB-S2/ACM


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•A Powerful Combination: Integrating Group QoS and DVB-S2/ACM

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iDirect: Tech Brief - QoS and DVB-S2/ACM

  1. 1. A Powerful Combination:Integrating Group QoS & DVB-S2/ACMSeptember 2009 13865 Sunrise Valley Drive, Herndon, VA 20171 Tel: +1 703.648.8000 +1 866.345.0983 • -1-
  2. 2. IntroductioniDirect’s Group Quality of Service (GQoS) provides a comprehensive set of powerful, state-of-the-artfeatures that allow Service Providers a significant increase in bandwidth management capabilities.This is especially important when prioritizing traffic for customers in a shared network environment -resulting in greater flexibility for traffic configuration and prioritization, more bandwidth savings andimproved service quality for customers. GQoS creates new sales opportunities for Service Providerswhere service plans can be matched to their customers’ unique and growing bandwidth needs andensure service quality for different applications as the networks expand.DVB-S2/ACM is also creating new opportunities for Service Providers. They can take advantage of themost efficient transmission scheme, DVB-S2, by combining multiple small networks into a single,larger carrier, bringing additional advantages to network design. Coupled with Adaptive Coding andModulation (ACM), each remote can operate at its most efficient modulation and coding (MODCOD)scheme, at any moment in time, depending on location within the satellite contour, antenna size, andatmospheric conditions. ACM evaluates current channel conditions and throughput requirementsthrough a return channel to determine the ideal modulation and FEC rate for each individual remoteand makes adjustments in real time. In short, ACM not only optimizes the bandwidth efficiency formaximum throughput on a remote-by-remote basis, but Service Providers avoid having to determine inadvance which modulation and coding should be used.With adaptive MODCODs comes the challenge of accurately delivering and pricing the differentservice levels that end-customers come to expect. Traditional pricing models no longer apply asbandwidth requirements vary significantly with adaptive MODCODs. This paper will briefly examine thechallenges of traditional bandwidth allocation and demonstrate the benefit of a tight ACM and GQoSintegration.Traditional Pricing ModelsService Level Agreements (SLAs) are based on Committed Information Rate (CIR) and percentavailability (uptime) while the service price is based on satellite bandwidth. CIR is the amount ofdedicated bandwidth assigned to a particular router to eliminate the need to contend for an opportunityto transmit regardless of how busy the network is. The bandwidth needed to meet the CIR variessignificantly based on the MODCOD used, which varies based on rain fade and each terminal.Service pricing prior to DVB-S2/ACM was based on the amount of satellite bandwidth needed toachieve a CIR designed around a reliable MODCOD operating in worst case conditions such as heavyrain fade. The satellite bandwidth price per remote was known since a fixed MODCOD was usedthroughout the network. However with DVB-S2/ACM, adaptive MODCODs vary constantly based onweather conditions, so the required bandwidth to provide a given CIR varies constantly as well.13865 Sunrise Valley Drive, Herndon, VA 20171Tel: +1 703.648.8000 +1 866.345.0983 • -2-
  3. 3. Figure 1. Adaptive Coding and ModulationWith DVB-S2 in ACM mode, the same amount of user data occupies less or more bandwidth,depending on the MODCOD at which it is transmitted. For example, user data transmitted at a higherMODCOD requires less bandwidth than it does at a lower MODCOD to guarantee a fixed CIR.Figure 2 shows the relative bandwidth required to deliver a fixed CIR across MODCODs. BW Required to Maintain Fixed CIR 600 400 Relative Bandwidth (kHz) 350 500 300 400 CIR (kbps) 250 Nominal 300 200 150 200 100 100 50 0 0 Figure 2. DVB-S2/ACM’s Varying Bandwidth Requirements Across MODCODs13865 Sunrise Valley Drive, Herndon, VA 20171Tel: +1 703.648.8000 +1 866.345.0983 • -3-
  4. 4. ExampleA remote location requires a fixed CIR of 256 Kbps. The nominal MODCOD is set at 8PSK 3/5 at ClearSky. With adverse weather conditions the MODCODs change and more bandwidth now is required tomaintain the fixed CIR of 256 Kbps. MODCODClear Sky 8PSK 3/5Rain Fade QPSK 3/5, requiring 50% more bandwidthHeavy Rain Fade QPSK 1/4, requiring almost 5 times more bandwidthIn this example, maintaining the same CIR at heavy rain fade requires almost five times the Clear Skybandwidth.It would be unfair to charge two remotes the same service price if they are operating at differentMODCODs where one remote may be consuming five times the bandwidth compared to the otherwhile still getting the same CIR. Even without ACM, Service Providers were not able to treat customerswith varying remote antenna sizes fairly. Networks were traditionally designed around worst-caseparameters, in this case the smallest antenna to account for the total needed bandwidth. Customerswho invested in larger antennas were not rewarded for utilizing less bandwidth compared to those withsmaller antennas.By tightly integrating GQoS and DVB-S2/ACM these challenges can be overcome and customers canbe treated more fairly.New Configuration ParametersWith the tight integration of ACM and GQoS comes the benefit of introducing new configurationparameters and options that were previously not easy to configure, operate or monitor.Nominal MODCOD ConfigurationThe Nominal operating point represents the MODCOD that the Service Provider bases the SLA on toprovide a CIR with a given availability to a customer.In a network with fixed remotes, the Service Provider can configure the Nominal operating point to bethe Clear sky operating point based on the link budget or could set it at a MODCOD lower than Clearsky to improve the CIR availability. In a mobile network, the Nominal operating point can be any pointin the beam coverage at which the Service Provider wants to guarantee a CIR and a given availability.iDirect’s iVantage NMS provides statistics on the operating point of each remote. The Service Providercan use these statistics to determine the percentage of time a remote is operating at its NominalMODCOD and at other MODCODs. Although independent of traffic, this allows Service Providers tocompare a remote’s actual operating point with its configured (or contractual) operating point andmake adjustments in the case of discrepancies.13865 Sunrise Valley Drive, Herndon, VA 20171Tel: +1 703.648.8000 +1 866.345.0983 • -4-
  5. 5. The configuration of a Nominal operating point allows the Service Provider to offer two new serviceofferings in a DVB-S2/ACM network: Fixed bandwidth Fixed CIR / Extended Information Rate (EIR)Fixed Bandwidth ConfigurationIn this configuration the Service Provider can base the pricing on the Nominal MODCOD andcorresponding satellite bandwidth used at an agreed upon Nominal operating point. The CIR andMaximum Information Rate (MaxIR) are limited to this configured point.When the remote goes into rain fade and the MODCODs change to a more conservative setting, theCIR and MaxIR are scaled down relative to their configured Nominal operating points. This provides agradual degradation in CIR/MaxIR during rain fade while consuming a fixed satellite bandwidth basedon the amounts consumed during the Nominal operating point.During Clear Sky the remote is allowed to operate at MODCODs higher than its Nominal operatingpoint but will not be rewarded with a higher CIR/MaxIR. Fixed Bandwidth Mode 600 400 Relative Bandwidth (kHz) 350 500 300 400 CIR (kbps) 250 Nominal 300 200 150 200 100 100 50 0 0 Figure 3. Total Bandwidth vs. Information Rate in Fixed Bandwidth Operation Fixed Bandwidth Benefits The Service Provider benefits from the savings in bandwidth during clear sky conditions while complying with the Service Level Agreement (SLA) of its customers. The Service Provider has the option to configure the Nominal operating point at Clear Sky or at a lower point to improve the availability of the CIR in a light rain fade. The end-user benefit comes from a fair pricing model by the Service Provider. End-users investing in larger antennas would be able to take advantage of lower service pricing if their13865 Sunrise Valley Drive, Herndon, VA 20171Tel: +1 703.648.8000 +1 866.345.0983 • -5-
  6. 6. operating point is at the higher efficiency MODCODs. Also the end-user has the option of experiencing a more gentle degradation in CIR during rain fade for a more affordable service pricing instead of signing up for a guaranteed CIR at severe rain fade.Fixed CIR/ EIR ConfigurationFor customers who need a fixed CIR under changing MODCODs and bandwidth conditions, ServiceProviders can now offer an Extended Information Rate (EIR) option, also referred to as rain fadeinsurance. EIR can be offered as a way to maintain CIR during rain fade of a particular remote or acritical application such as VoIP.The configured EIR Minimum determines the lowest MODCOD that will honor the CIR during rain fade.When operating at or above the EIR Minimum, the system always attempts to allocate requestedbandwidth in accordance with the CIR and MaxIR settings, regardless of the current MODCOD atwhich the remote is operating. The customer will be guaranteed the CIR during rain fade down to theEIR Minimum. Fixed CIR - EIR Mode 600 400 Relative Bandwidth (kHz) 350 500 300 400 CIR (kbps) 250 Nominal EIR Min 300 200 150 200 100 100 50 0 0 Figure 4. EIR: Total Bandwidth vs. Information Rate as MODCOD VariesExampleIn Figure 4, the Nominal MODCOD is configured at 8PSK 3/5 based on the expected Clear Skyoperating point for the remote. The system will maintain the CIR for the remote during rain fade downto the configured EIR Min at QPSK 3/5. Note the additional bandwidth required to maintain the CIR inrain fade. If the remote goes into a deeper rain fade resulting in operation below the EIR Min, its CIRwill be scaled down relative to the satellite bandwidth required at its Nominal MODCOD.13865 Sunrise Valley Drive, Herndon, VA 20171Tel: +1 703.648.8000 +1 866.345.0983 • -6-
  7. 7. Fixed CIR/ EIR Benefits The Service Provider can benefit from this option by offering a “rain fade Insurance” option for customers desiring to maintain their CIR during rain fade and willing to pay for it. The pricing of this option can be based on how much rain fade margin the end-user requires which determines the EIR Minimum. Services can be charged a premium since more bandwidth is needed during rain fade. End-users can benefit from having higher availability of CIR during rain fade for their business critical applications or locations. The EIR option let Service Providers offer a fair pricing model to end-users.Bandwidth Allocation Fairness in ContentionWith the tight integration of GQoS and ACM comes the possibility for Service Providers to offeradditional fairness in bandwidth allocation during times of contention to their customers. It gives theService Provider the flexibility to maximize the performance of a network in a fair and flexible manner.There are two options the Service Provider can choose to implement: Allocation Fairness Relative to CIR Allocation Fairness Relative to MODCODAllocation Fairness Relative to CIRThis configuration option allows the allocation of the available bandwidth during contention relative tothe configured CIR of each customer. The same fairness scheme applies to the bursting round ofbandwidth allocation when all CIRs are satisfied.ExampleRemote 1 CIR: 256 kbpsRemote 2 CIR: 512 kbps (Both Remotes operating at the same Nominal MODCOD)Scenario A Scenario B Allocation Fairness Allocation Fairness450K Available for 450K Available forthe Service Group Service Group Relative to CIR - the Service Group Service Group Relative to CIR - Disabled Enabled Remote 1 Remote 2 Remote 1 Remote 2 (CIR = 256K) (CIR = 512K) (CIR = 256K) (CIR = 512K) Allocation: 225K Allocation: 225K Allocation: 150K Allocation: 300KIn scenario A, Remote 1 and Remote 2 both operate at the same Nominal MODCOD. Remote 1 isconfigured with a CIR or 256 Kbps while Remote 2 is configured with a CIR of 512 Kbps. The Service13865 Sunrise Valley Drive, Herndon, VA 20171Tel: +1 703.648.8000 +1 866.345.0983 • -7-
  8. 8. Provider may choose to split the total available bandwidth of 450K equally during contention until thelower CIR is satisfied which results in both Remotes 1 and Remote 2 getting a bandwidth allocation of225 Kbps.In scenario B, the Service Provider allocates the bandwidth proportionally to the remote’s CIR. In thiscase Remote 1 gets half of the bandwidth of Remote 2.While some corporate networks may want to satisfy remote sites with small CIRs during contention likein scenario A, Service Providers generally would increase the customer’s satisfaction by allocating thebandwidth more fairly relative to the contracted CIR like in scenario B.Allocation Fairness Relative to MODCODThis configuration option allows the allocation of the available bandwidth during contention in a waythat provides equal information rates to remotes configured with the same CIR regardless of theirconfigured Nominal MODCOD. The same fairness scheme applies to the bursting round of bandwidthallocation when all CIRs are satisfied.ExampleRemote 1 8PSK 3/4 Nominal MODCOD, CIR: 1 MbpsRemote 2 QPSK 3/4 Nominal MODCOD, CIR: 1 Mbps (R2 requires 1.5 times more bandwidth than R1 for same CIR)Available bandwidth Equivalent of 1.65 Mbps @ 8PSK ¾Scenario A: Split available satellite bandwidth Scenario B: Split available bandwidth toevenly achieve equal Info Rate1.65M @ 8PSK ¾ Allocation Fairness 1.65M @ 8PSK ¾ Allocation FairnessAvailable for the Service Group Relative to MODCOD Available for the Service Group Relative to MODCODService Group - Disabled Service Group - Enabled Remote 1 Remote 2 Remote 1 Remote 2 (CIR = 1M) (CIR = 1M) (CIR = 1M) (CIR = 1M) Nominal 8PSK 3/4 Nominal QPSK 3/4 Nominal 8PSK 3/4 Nominal QPSK 3/4 Allocation: 825K Allocation: 550K Allocation: 660K Allocation: 660KIn this example, Remote 1 and Remote 2 are both configured with a CIR or 1 Mbps. Remote 1 isoperating at a Nominal MODCOD of 8PSK ¾ while Remote 2 is operating at a Nominal MODCOD ofQPSK ¾. Note that QPSK ¾ requires about 1.5 times the bandwidth of 8PSK ¾ to deliver the sameCIR. In scenario A the Service Provider splits the satellite bandwidth equally during contention, whichresults in Remote 1 getting 825 Kbps and Remote 2 getting 550 Kbps. In scenario B the ServiceProvider provides the same Information Rate to Remote 1 and Remote 2, 660 Kbps in this case. Thisresults in Remote 2 utilizing 1.5 times the satellite bandwidth of Remote 1.13865 Sunrise Valley Drive, Herndon, VA 20171Tel: +1 703.648.8000 +1 866.345.0983 • -8-
  9. 9. While some Service Providers for corporate networks may elect to operate in scenario A to favorremotes operating at more efficient MODCODs, Service Providers that encourage end users to investin larger antennas through their service pricing model prefer scenario B. In such case, the pricingmodel reflects the additional bandwidth required at lower MODCODs and fairness relative toMODCODs is more appropriate.These different allocation and configuration options enable the Service Provider for the first time toimplement more fairness algorithms and start offering a wider selection of pricing options for the end-customer. This ultimately will result in increased customer satisfaction.ConclusioniDirect’s full integration of DVB-S2/ACM with GQoS provides maximum efficiency, flexibility andallocation fairness for the Service Provider that results in increased customer satisfaction and moreservice options for the customers. Service Providers can create a wider selection of service offeringsbased on their DVB-S2/ACM service that ultimately translates into an increased revenue opportunityand a unique competitive advantage. This is an opportunity that is only made possible through the tightintegration of DVB-S2/ACM and GQoS and that cannot be achieved with an external QoS device.These benefits maximize the bandwidth efficiency of a Service Provider’s network and enable them tomaximize revenue and increase end-customer satisfaction.13865 Sunrise Valley Drive, Herndon, VA 20171Tel: +1 703.648.8000 +1 866.345.0983 • -9-